Measurements of the magnetic form factor of the proton in the timelike region at large momentum transfer

The cross section for the reaction p̄→pe⁺e^- has been measured at $s=8.8,$ $10.8,$ $12.4,$ $13.1,$ and 14.4 GeV² by Fermilab experiment E835. A non-magnetic spectrometer is used to identify the e⁺e^- final states generated by the antiproton beam intersecting an internal hydrogen gas jet target. From the analysis of the 144 observed events, new high-precision measurements of the proton magnetic form factor for timelike momentum transfers are obtained.